\documentclass{article}

\usepackage{booktabs}
\usepackage{dcolumn}

\newcolumntype{d}{D{.}{.}{5.5}}
\newcolumntype{C}{>{\centering}p}

\begin{document}

\begin{table}[htp]
	\caption{}
	\centering
	\begin{center}
		\begin{tabular}{p{1.25in}ddd}
			\toprule
			\multicolumn{1}{C{1in}}{\shortstack{Group}} & \multicolumn{1}{C{0.75in}}{\shortstack{Weight                                                     \\(g)}} &    \multicolumn{1}{C{1in}}{\shortstack{Glucose\\(mg/l)}} & \multicolumn{1}{C{2in}} {\shortstack{Glycosylated protein\\(nmol/mg protein)}}\\
			\midrule
			Control                                     & 544.5                                         & 908.0                           & 17.8            \\
			Diabetic                                    & 331.2{$^{***}$}                               & 5736.0{$^{***}$}                & 32.10{$^{***}$} \\
			Diabetic+GT                                 & 343.9{$^{***}$}                               & 4037.0{$^{***}\dagger\dagger$ } & 24.87{$^{***}$} \\
			\bottomrule
		\end{tabular}
	\end{center}
	\label{tbl:results}\\
\end{table}

\end{document}
